MetallicFuelWastageDegradationFunction

Description

The MetallicFuelWastageDegradationFunction calculates a degradation factor function based on a VectorPostprocessor that tracks either FCCI wastage thickness on the inner surface of the cladding or coolant-cladding chemical interaction (CCCI) wastage thickness on the outer surface of the cladding. The degradation factor function can then be used by BISON's cladding mechanical property Materials objects to account for mechanical strength degradation caused by FCCI and CCCI. The Materials objects that are compatible with MetallicFuelWastageDegradationFunction include HT9ElasticityTensor, D9ElasticityTensor, SS316ElasticityTensor, HT9CreepUpdate, D9CreepUpdate, SS316CreepUpdate, and their corresponding AD variants.

Controlled by the input parameter wastage_type, this Function object can handle either FCCI (ID) or CCCI (OD). If the degradation effects of both FCCI and CCCI need to be taken into consideration within a single simulation, MetallicFuelWastageDegradationFunction needs to occur twice in the input file with different sub-block names to provide both degradation factors.

For the FCCI wastage at a given axial position of the FCCI thickness VectorPostprocessor, assuming the FCCI thickness is , the degradation factor function, , has the following expression in the radial direction,

where is the degradation factor of unaffected cladding (which is usually a trivial value of 1.0), is the degradation factor of cladding consumed by FCCI wastage, is the radial position of the inner cladding surface, and is the radial position of the outer cladding surface. Optionally, a transition width, , can be set up to connect the FCCI region and an unaffected region using a sine curve (see Figure 1).

Figure 1: The radial profile of the FCCI degradation factor function at a given axial position.

For the CCCI wastage at a given axial position of the CCCI thickness VectorPostprocessor, assuming the CCCI thickness is , the degradation factor function, , has the following expression in the radial direction,

(1)

where is the degradation factor of unaffected cladding (which is usually a trivial value of 1.0), is the degradation factor of cladding consumed by FCCI wastage, is the radial position of the inner cladding surface, and is the radial position of the outer cladding surface. Optionally, a transition width, , can be set up to connect the CCCI region and an unaffected region using a sine curve (see Figure 2).

Figure 2: The radial profile of the FCCI degradation factor function at a given axial position.

The selection of () is important for this degradation factor approach to provide reliable results. To identify the optimized value of (), a HT9 pressurized tube with both FCCI and CCCI wastage layers is simulated with MetallicFuelWastageDegradationFunction. The results are compared with those of a HT9 pressurized tube with both FCCI and CCCI wastage layers removed from the mesh. The comparison is shown in Figure 3. It is clear that () = 0.001 leads to differences in both CDF (cumulative damage fraction) and hoop strain lower than 7%. The 0.001 is set as the default value of the degradation factor.

Figure 3: Effect of degradation factor on cumulative damage fraction (CDF) and hoop strain calculation.

Additionally, in order to calculate the degradation function, multiple cladding geometry parameters are required, such as cladding thickness, cladding outer radius, and top/bottom axial positions of the cladding (excluding end caps). The MetallicFuelWastageDegradationFunction object can directly get these parameter from mesh metadata if FuelPinMeshGeneratorFIPD is used to create the mesh. Otherwise, those parameters need to be input manually.

Example Input Syntax

[Functions<<<{"href": "../../syntax/Functions/index.html"}>>>]
  [id_degradation]
    type = MetallicFuelWastageDegradationFunction<<<{"description": "Generate a cladding degradation factor function based on two columns of a VectorPostprocessor that tracks the axial profile of either FCCI or CCCI wastage thickness.", "href": "MetallicFuelWastageDegradationFunction.html"}>>>
    vectorpostprocessor_name<<<{"description": "The name of the VectorPostprocessor that you want to use"}>>> = id_wastage
    argument_column<<<{"description": "VectorPostprocessor column tabulating the abscissa of the sampled function."}>>> = y
    value_column<<<{"description": "VectorPostprocessor column tabulating the ordinate (function values) of the sampled function."}>>> = wastage_thickness
    cladding_start<<<{"description": "Start (bottom) axial position of hollow cladding."}>>> = 2.24e-3
    cladding_end<<<{"description": "End (top) axial position of hollow cladding."}>>> = 102.55e-3
    cladding_thickness<<<{"description": "Thickness of the cladding before wastage formation."}>>> = 3.81e-4
    cladding_outer_radius<<<{"description": "Outer radius of the cladding before wastage formation."}>>> = 4.4e-3
  []
[]

Input Parameters

Input Files

• (assessment/metallic_fuel/FBTA/analysis/fbta_run/FBTA_base.i)
• (assessment/metallic_fuel/FBTA/analysis/steady_state/common_inputs/test_base.i)
• (assessment/metallic_fuel/EBRII/X447/analysis/legacy/x447_base.i)
• (assessment/metallic_fuel/EBRII/X447/analysis/enhancement/x447_enh_base.i)
• (test/tests/metallic_fuel_cladding_degradation/test_od.i)
• (test/tests/metallic_fuel_cladding_degradation/test_id_meshmetadata.i)
• (assessment/metallic_fuel/EBRII/X423/analysis/x423_vp_base.i)
• (assessment/metallic_fuel/EBRII/X423/analysis/x423_lm_base.i)
• (test/tests/metallic_fuel_cladding_degradation/test_id_missing_geom.i)
• (test/tests/metallic_fuel_cladding_degradation/test_id.i)
• (assessment/metallic_fuel/WPF/analysis/X425_T418/X425_base.i)
• (assessment/metallic_fuel/FBTA/analysis/steady_state/AK181/181193/IFR1_181193.i)
• (assessment/metallic_fuel/WPF/analysis/FM-1/FM_base.i)